Orders of Goegraphic Magnitude
Throughout this text we discuss geographic studies confined to size,or orders of geographic magnitude, between these two extremes. Although the variations are considerable, the geographer is concerned with a narrow ‘window’ within the scale of scientific inquiry. In the figure in Box 1.C on ‘Orders of geographic magnitude ’the main areas of scientific inquiry are plotted along a centimeter scale. Exponential notation is used in order to present a large range of variation on the same diagram.
The scale extends from the microworld of the atomic physicist,studying cosmic rays with wavelengths of about 10 cm ,to the radio astronomer,studying galaxies with diameters of 10 cm and more.By comparison,the geographer’s world is confined to a narrow band along the middle range of the scale . The smallest objects studied are about the size of a beach or a city block. They are not less than a few hundred metres across or approximately 10 cm. Conversely , the largest object studied is the earth, with an equatorial circumference of around 40000 km or about 10 cm. There is therefore a range of 5,i.e.10 minus 10 in the ‘size’ of objects studied by geographers. To put this another way, the real world shown in the atlas section is around 100000 times greater in diameter than the world of the beach.
We use the orders of geographic magnitudes described in the box to keep in focus the areas we are dealing with. These orders of magnitude serve a purpose similar to that of the astronomer’s orders of star brightness and are a happy substitute for the jumble of scales usually used in geography books. They remind us that we are dealing not with the real world but with reduced and simplified models of it.